The non-invasive prenatal test is a relatively new test. It is a blood test taken from the mother which detects fetal cells. The fetal cells are separated from the maternal cells and tested for certain chromosomes. Generally chromosomes 21, 18, 13, X and Y are tested. The test can be done any time after 10 weeks gestation. It gives similar results to an amniocentesis. The difference between this test and an amniocentesis is that it is non-invasive, in other words, it only requires a maternal blood test and no needles are required that may potentially harm the baby.
The drawback of this test is its expense. Currently in Australia there are four companies that offer the test, all of which have labs outside of Australia. Blood needs to be taken at specified pathology collection centres and sent to overseas labs. As a result of this, it often takes 10-14 days for the results to come back.
This is still an improvement on the current test of amniocentesis where preliminary results are seen as early as 48 hours, but final results are not seen until up to 3-4 weeks later. The cost of the test ranges from$600 – $1000 depending on which company is used.
For most chromosomes tested the results are accurate to greater than 99%. This test is a good option for women who have tested high risk for the combined first trimester screen (nuchal translucency scan) or women who are older or have an established family and do not want an affected child.
This means that if the test is done as early as ten weeks, the results are usually at hand by 12 weeks at which time a termination of pregnancy would be much simpler than performing the same at 20 weeks gestation.
I tend to offer this test to all patients if they so desire. Having said that, the majority of patients are usually happy with the current level of testing as this gives adequate reassurance and confidence to expectant couples.